Ink jet printing is extremely popular in a wide variety of industries. Typically, ink jet printing is accomplished through the use of a print head. The print head includes a plurality of orifices each capable of depositing an ink drop upon a substrate to form a predetermined pattern, such as an image, text, and the like. The plurality of orifices contained in the print head are arranged in rows and columns and are each capable of depositing an ink drop to a defined pixel position grid (also, defined as rows and columns) upon a substrate. This row and column arrangement of the orifices typically does not span the full number of rows or the full number of columns in the pixel position grid. Consequently, the print head and the substrate must be moved relative to each other to create the desired output to be printed.
As is known in the art, ink jet printing may be used in printing upon elongated substrates, such as paper rolls or sheets. To this end, the print head is often scanned or driven in a direction laterally across the substrate as the substrate is driven in a longitudinal direction. The substrate is typically stopped at predetermined steps according to separate encoding systems that accurately track the longitudinal movement of the substrate. Typically, at each step, a line of ink is deposition along a row of pixels, which is often referred to as a print line.
In low resolution printing, a first section of the image is printed across the substrate to define the entire row and a length of the columns. The substrate is then advanced a step and another entire row and an additional length of the columns is deposited. This process continues until the image is completed.
In high resolution printing, the density of the ink deposits in the pixel grid is increased to provide improved resolving power. To an extent, this can be achieved by manufacturing the print head with a single lateral line of more closely spaced orifices. However, it should be understood that there are limits to the minimum spacing between adjacent orifices that can be achieved with today's manufacturing systems.
Print heads can be made as wide as the area to be printed to promote single pass printing. In this arrangement, the substrate is moved longitudinally as the print head is held stationary. An entire row of ink is deposited at a time to provide the single pass capability.
Attempts have been made to improve the resolution of existing print head designs through the use of interlace configurations. Specifically, as seen in FIG. 1, these conventional designs employ a plurality of print heads that are arranged in multiple rows and overlapped or interlaced to stagger the print heads of each row relative to adjacent rows. In this regard, the resolution of the printing system is improved despite mechanical manufacturing limitations. However, these arrangement also suffer from a number of disadvantages, such as their sensitivity to yaw angle alignment of the substrate relative to the print head, the clumping of ink drops on non-absorbent substrates, and additionally the inability to nest adjacent print heads directly next to each other. These disadvantages will be discussed in further detail below.